The invention is related to the field of field emitter arrays, and in particular to dense arrays of field emitters using vertical ballasting structures. Each field emitter uses a vertical ballasting structure.
Electrons are field emitted from the surface of metals and semiconductors when the potential barrier that holds electrons within the material is deformed by the application of a high electrostatic field. Typically high surface electrostatic fields are obtained by the application of a voltage between a gate structure and a high aspect ratio structure with nano-meter scale tip radius which usually has Gaussian or log-normal distribution. Due to the exponential dependence on tip radius, emission currents are extremely sensitive to tip radii variation. Consequently, only a small fraction of the tips in an array emit electrons when sufficient voltage is applied between the gate structure and the emitters. Attempts to increase the emission current by increasing the voltage often result in burnout and shifting of the operating voltage to higher voltages. Therefor; it is difficult to obtain uniform or high currents from field emitter arrays (FEAs). Spatial non-uniformity can be substantially reduced if the emitters are ballasted as demonstrated in the past with groups of emitters.
The use of large resistors in series with the field emitters is an unattractive ballasting approach because of the resulting low emission currents and power dissipation in the resistors.